Active vibration damping device

Abstract

To provide an active vibration damping device which inhibits performance deterioration caused by precipitation of a magnetic powder of a magnetorheological fluid in a liquid chamber without increasing a volumetric capacity of the liquid chamber to be filled with the magnetorheological fluid.SOLUTION: An active vibration damping device has: an outer cylinder 2; an inner cylinder 3 arranged on an inner peripheral side of the outer cylinder 2; an electromagnetic coil 12; a first magnetic material 6 and a second magnetic material 7; a first liquid chamber 15 filled with a magnetorheological fluid 20b; a second liquid chamber 21 located adjacent to the first liquid chamber 15 and filled with a liquid 20a; an outer cylinder flange 4; and an inner cylinder flange 5 which is arranged spaced apart from the outer cylinder flange 4 in an axial direction. The first liquid chamber 15 and the second liquid chamber 21 are partitioned from each other in the axial direction by a flexible member 14. The second liquid chamber 21 is formed so as to be sandwiched between the inner cylinder flange 5 and the outer cylinder flange 4, and portions of the first liquid chamber 15 form flow passages of the magnetorheological fluid 20b that are located on a magnetic circuit.SELECTED DRAWING: Figure 4A

Description

[Technical Field]

[0001] The present invention relates to an active vibration isolation device. [Background technology]

[0002] In recent years, efforts to provide access to sustainable transport systems that take into consideration vulnerable transport users such as the elderly, people with disabilities, and children have been gaining momentum. To achieve this, we are focusing on research and development to further improve transport safety and convenience through the development of vehicle livability. Active vibration isolation devices have been proposed for use in subframe mounts, suspension bushings, and the like, with the aim of improving vehicle comfort by suppressing noise and vibration within the vehicle cabin (see, for example, Patent Document 1). Specifically, this active vibration isolation device has two fluid chambers filled with magnetorheological fluid connected by a flow path, and is equipped with an excitation coil that forms a magnetic path in a direction intersecting the flow path. With this active vibration isolation device, the magnetorheological fluid attempts to flow through the flow path from one fluid chamber to the other in response to the magnitude of the input vibration amplitude. At this time, the active vibration isolation device controls the flow of the magnetorheological fluid by varying the magnetic flux density generated by the excitation coil. This allows the active vibration isolation device to exhibit flexible damping characteristics in response to the magnitude of the input vibration amplitude. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent Publication No. 2021-71117 Summary of the Invention [Problem to be solved by the invention]

[0004] In conventional active vibration isolation devices (see, for example, Patent Document 1), the volume of the liquid chamber can be increased to improve response performance to input vibration amplitude, but this increases the amount of relatively heavy and expensive magnetorheological fluid that is filled into the liquid chamber, which contains magnetic powder. This increases the manufacturing cost of the active vibration isolation device and creates new problems, such as an increase in the weight of the vehicle in which it is installed. Furthermore, with an active vibration isolation device, as the amount of magnetorheological fluid used increases, the absolute amount of magnetic powder contained in the magnetorheological fluid that settles also increases, which could result in a decrease in the performance of the active vibration isolation device.

[0005] The present invention aims to provide an active vibration isolation device that can improve response performance to external forces such as input vibrations and loads without increasing the volume of the liquid chamber filled with magnetorheological fluid, and that can also suppress performance degradation due to the settling of magnetic powder in the magnetorheological fluid in the liquid chamber, thereby contributing to the development of sustainable transportation systems. [Means for solving the problem]

[0006] The present invention provides an active vibration damping device having an outer tube, an inner tube arranged on the inner periphery of the outer tube, a magnetic field generating unit that generates a magnetic field, a magnetic body that forms a magnetic path by the magnetic field, a first liquid chamber filled with a magnetorheological fluid, and a second liquid chamber adjacent to the first liquid chamber and filled with liquid, and is characterized in that it comprises an outer tube flange extending radially outward from one axial end of the outer tube, and an inner tube flange that extends radially outward from the inner tube and is arranged spaced apart from the outer tube flange in the axial direction, the first liquid chamber and the second liquid chamber being separated in the axial direction by a flexible member, the second liquid chamber being formed so as to be sandwiched between the inner tube flange and the outer tube flange, and a portion of the first liquid chamber forming a flow path for the magnetorheological fluid located on the magnetic path. [Effects of the Invention]

[0007] The active vibration damping device of the present invention can improve response performance to external forces such as input vibrations and loads without increasing the volume of the liquid chamber filled with magnetorheological fluid, and can also suppress performance degradation due to the settling of magnetic powder in the magnetorheological fluid in the liquid chamber. [Brief explanation of the drawings]

[0008] [Figure 1] 1 is an overall perspective view of a subframe equipped with an active vibration isolation device according to an embodiment of the present invention; [Figure 2] 1 is an overall perspective view of an active vibration isolation device according to an embodiment of the present invention; [Figure 3] 1 is an exploded perspective view of an active vibration isolation device according to an embodiment of the present invention. [Figure 4A] FIG. 3 is a partial perspective view of the active vibration isolation device including the IVA-IVA cross section of FIG. 2. [Figure 4B] 4 is a partial perspective view of the active vibration isolation device including the cross section IVB-IVB of FIG. 2. FIG. [Figure 4C] FIG. 3 is a partial perspective view of the active vibration isolation device including the IVC-IVC cross section of FIG. 2. [Figure 5A] FIG. 3 is a partial perspective view of the active vibration isolation device including the VA-VA cross section of FIG. 2. [Figure 5B] 3 is a partial perspective view of the active vibration isolation device including the VB-VB cross section of FIG. 2. FIG. [Figure 5C] 3 is a partial perspective view of the active vibration isolation device including the VC-VC cross section of FIG. 2. FIG. [Figure 6A] 5A and 5B are explanatory diagrams illustrating the operation of the active vibration isolation device when vibrations or the like are input in the axial direction of the active vibration isolation device. [Figure 6B] 10 is an explanatory diagram of the operation of the active vibration damping device, showing how the magnetorheological fluid flows in the first fluid chamber when vibration or the like is input in the axial direction of the active vibration damping device. FIG. [Figure 6C] 10 is an explanatory diagram of the operation of the active vibration isolation device when vibrations or the like are input in a direction in which the inner cylinder of the active vibration isolation device is gouged relative to the outer cylinder. FIG. [Figure 6D]10 is an explanatory diagram illustrating the operation of an active vibration isolation device, showing how a magnetic path is formed by a magnetic field generated by an electromagnetic coil. FIG. [Figure 6E] 5 is a schematic diagram showing the behavior of magnetic powder when a magnetic field is applied to an orifice of a first liquid chamber. FIG. [Figure 7A] FIG. 10 is a layout diagram of a second liquid chamber and an air chamber of an active vibration damping device according to a first modified example. [Figure 7B] FIG. 10 is a layout diagram of a first fluid chamber of an active vibration damping device according to a first modified example. [Figure 8] FIG. 10 is a diagram illustrating the configuration of an active vibration isolation device according to a second modified example. [Figure 9A] FIG. 10 is a vertical cross-sectional view of an active vibration isolation device according to a third modified example. [Figure 9B] FIG. 11 is an exploded perspective view of an active vibration isolation device according to a third modified example. DETAILED DESCRIPTION OF THE INVENTION

[0009] Next, an active vibration isolation device according to an embodiment of the present invention will be described in detail with reference to the accompanying drawings. In the following, we will use an active vibration isolation device applied to a vehicle subframe as an example, but the present invention is not limited to this and can also be applied to vehicle noise and vibration isolation devices such as mounting bushes that are placed between components connected to the vehicle frame. First, the overall configuration of a subframe to which the active vibration isolation device of this embodiment is applied will be described, and then the active vibration isolation device will be described in more detail.

[0010] <Subframe> Fig. 1 is an overall perspective view of a subframe equipped with an active vibration isolation device according to an embodiment of the present invention. Note that the up, down, left, right, front, and rear directions in the following description are based on the directions of arrows in Fig. 1, which correspond to the up, down, left, right, front, and rear directions of a vehicle.

[0011] The subframe 30 shown in FIG. 1 is attached to the vehicle body side, such as a rear side frame (not shown), of the vehicle, and has a structure that supports a suspension arm (not shown). As shown in FIG. 1, the subframe 30 has a lattice shape in plan view. Specifically, the subframe 30 comprises a front cross member 31 extending in the vehicle width direction (left-right direction), a rear cross member 32 extending in the vehicle width direction (left-right direction) behind the front cross member 31, and a pair of left and right side members 33 connected to both ends of the front cross member 31 and the rear cross member 32 in the vehicle width direction and extending in the fore-and-aft direction.

[0012] Each of the side members 33 is curved so as to convex inward in the vehicle width direction in a plan view. That is, each of the side members 33 is curved so as to be displaced outward in the vehicle width direction as it moves forward from the joint with the front cross member 31. Also, each of the side members 33 is curved so as to be displaced outward in the vehicle width direction as it moves rearward from the joint with the rear cross member 32. Collar members 34 are attached to the front and rear ends of the side members 33 by welding or the like.

[0013] The collar member 34 is formed of a cylindrical body that is open at the top and bottom. A bushing 35 is inserted into the inside of the collar member 34. The bushing 35 is fixed to the collar member 34 by welding or the like. The support shaft 36 of the bush 35 protruding upward is fastened to a rear side frame (not shown). As a result, the subframe 30 is supported in a floating manner on the rear side frame (not shown) via the bush 35. The bushing 35 is the active vibration isolation device of this embodiment, and will hereinafter be referred to as the active vibration isolation device 1. The support shaft 36 is inserted into and supported by a hole 3a (see FIG. 2) of an inner cylinder 3 (see FIG. 2) to be described later.

[0014] <Active vibration isolation device> Fig. 2 is an overall perspective view of the active vibration damping device 1 according to this embodiment. Fig. 3 is an exploded perspective view of the active vibration damping device 1. In Fig. 2, the second liquid chamber 21 and the air chamber 13 defined inside the elastic body 8 are depicted by hidden lines (dotted lines).

[0015] As shown in FIG. 2, the active vibration isolation device 1 has a cylindrical outer shape. Hereinafter, the direction along the axis Ax of this cylindrical active vibration isolation device 1 may be simply referred to as the "axial direction." Furthermore, the radial direction of the active vibration isolation device 1 may be simply referred to as the "radial direction," and the circumferential direction of the active vibration isolation device 1 may be simply referred to as the "circumferential direction."

[0016] As shown in FIG. 2, the active vibration isolation device 1 includes an outer cylinder 2, an outer cylinder flange 4, an inner cylinder 3, an inner cylinder flange 5, and an elastic body 8. As shown in FIG. 3, the active vibration isolation device 1 further includes a flexible member 14, a first magnetic body 6, a second magnetic body 7, an electromagnetic coil 12 (magnetic field generating unit), and a spacer 9.

[0017] As shown in FIG. 2, the outer cylinder 2 is formed of a cylindrical body. The outer cylinder flange 4 is formed of an annular plate that extends in a flange-like shape radially outward from one end of the outer cylinder 2 in the axial Ax direction. The outer cylinder flange 4 is molded integrally with the outer cylinder 2. As shown in FIG. 2, the inner cylinder 3 is disposed on the inner peripheral side of the outer cylinder 2. The cross section of the inner cylinder 3 has an oval track shape. Specifically, the cross section of the inner cylinder 3 has an oval shape consisting of a pair of straight line segments extending parallel to each other and a pair of arcs connected to both ends of the pair of straight line segments. The cross section of the hole 3a formed inside the inner cylinder 3 has a perfect circular shape. That is, the inner cylinder 3 is thicker in the longitudinal direction of the cross section than in the lateral direction.

[0018] Fig. 4A is a partial perspective view of the active vibration isolation device including the IVA-IVA cross section of Fig. 2. Fig. 4B is a partial perspective view of the active vibration isolation device including the IVB-IVB cross section of Fig. 2. Fig. 4C is a partial perspective view of the active vibration isolation device including the IVC-IVC cross section of Fig. 2. 4A, the inner cylinder flange 5 is formed of an annular plate that extends in a flange-like shape radially outward from one end of the inner cylinder 3 in the axial Ax direction. The inner cylinder flange 5 is molded integrally with the inner cylinder 3. The inner cylinder flange 5 is disposed at a distance from the outer cylinder flange 4 in the axial direction of the inner cylinder 3 .

[0019] The inner cylinder flange 5 also has a stepped wall 5a midway as it extends radially outward. That is, the inner cylinder flange 5 bends midway as it extends radially outward, away from the outer cylinder flange 4, extends in the axial direction, and then bends again so as to extend radially outward. A protruding portion 6a of the first magnetic body 6, which will be described later, is accommodated radially inside this stepped wall 5a.

[0020] 4A, a slit S1 is formed in the inner cylinder flange 5 so that a second liquid chamber 21 (described later) faces the flexible member 14. The slit S1 extends in the circumferential direction of the inner cylinder flange 5 so as to correspond to the second liquid chamber 21. 4C, a slit S2 is formed in the inner tube flange 5 so that an air chamber 13 (described later) faces the flexible member 14. The slit S2 extends in the circumferential direction of the inner tube flange 5 so as to correspond to the air chamber 13.

[0021] The outer cylinder 2, inner cylinder 3, outer cylinder flange 4, and inner cylinder flange 5 are assumed to be made of a non-magnetic material. Examples of non-magnetic materials include, but are not limited to, aluminum alloys, non-ferritic SUS, and copper. (0020) As shown in FIG. 4A, outer cylinder flange 4 and inner cylinder flange 5 are bonded together by vulcanization bonding with elastic body 8 made of synthetic rubber. 4C, the elastic body 8 vulcanization-bonds the outer tube 2 and the inner tube 3. Specifically, the elastic body 8 vulcanization-bonds the outer surface of the thicker portion of the inner tube 3 to the inner circumferential surface of the outer tube 2 that faces this outer surface. That is, in correspondence with the cross-sectional shape of the inner tube 3 described above, the outer surface that forms the arc portion of the oval track shape and the inner circumferential surface of the outer tube 2 are vulcanization-bonded by the elastic body 8.

[0022] However, as shown in FIGS. 4A and 4B, the flat outer surface of the inner cylinder 3 that forms the straight portion of the oval track shape is not directly vulcanization bonded to the inner peripheral surface of the outer cylinder 2 by the elastic body 8. That is, the joints between the inner peripheral surface of the outer cylinder 2 and the outer surface of the inner cylinder 3 by the elastic body 8 are limited to two locations spaced apart by a phase of 180 degrees when viewed in the direction of the axis Ax.

[0023] As shown in FIG. 4A, elastic body 8 vulcanization-bonds outer cylinder flange 4 and inner cylinder flange 5 with a predetermined distance between them. As shown in FIG. 4A, the elastic body 8 defines a second liquid chamber 21 between the outer cylinder flange 4 and the inner cylinder flange 5. Furthermore, the elastic body 8 defines an air chamber 13 between the outer cylinder flange 4 and the inner cylinder flange 5, as shown in FIG. 4C.

[0024] Next, the second liquid chamber 21 (see FIG. 4A) and the air chamber 13 (see FIG. 4C) will be described. 4A, the second liquid chamber 21 is formed as a space that is long in the axial direction in a cross-sectional view that crosses the second liquid chamber 21 in the radial direction. Specifically, the cross-sectional shape of the second liquid chamber 21 is formed so that the radial width gradually increases from the outer cylinder flange 4 side toward the inner cylinder flange 5 side. As shown in FIG. 4A, the second liquid chamber 21 faces the flexible member 14 via a slit S1 formed in the inner cylinder flange 5.

[0025] FIG. 5A is a partial perspective view of the active vibration isolation device 1 including the VA-VA cross section of FIG. 5A, two second liquid chambers 21 are formed in the circumferential direction of the inner cylinder flange 5. Specifically, the second liquid chambers 21 are arranged to face each other with the axis Ax therebetween. In other words, the second liquid chambers 21 are arranged 180 degrees apart from each other in the circumferential direction. In this embodiment, the second liquid chamber 21 extends in an arc shape in the circumferential direction. 4A and 5A, the second fluid chamber 21 is filled with a liquid 20a, which is a medium for transmitting vibrations, etc. As the liquid 20a, known hydraulic oils such as silicone oil and ester oil can be suitably used.

[0026] Next, the air chamber 13 (see FIG. 4C) will be described. As shown in FIG. 4C, the air chamber 13 is defined by a wall thickness thinner than the wall thickness of the elastic body 8 that defines the second liquid chamber 21 (see FIG. 4A). 5A, two air chambers 13 are arranged adjacent to the second liquid chambers 21 in the circumferential direction of the active vibration damping device 1. In other words, the air chambers 13 and the second liquid chambers 21 are arranged alternately in the circumferential direction of the active vibration damping device 1. As shown in FIG. 4C, the air chamber 13 faces the flexible member 14 via the slit S2 formed in the inner cylinder flange 5.

[0027] As shown in Fig. 5A, a connecting wall 13a is formed on the outer periphery of the air chamber 13 so as to circumferentially connect the outer periphery walls 21a of adjacent second liquid chambers 21. As shown in Fig. 4C, this connecting wall 13a extends in the circumferential direction on the outer periphery of the flexible member 14 and covers the air chamber 13 from the outer periphery. As shown in FIG. 5A, the connecting wall 13a is formed in a film shape made of an elastic body 8 that is thinner than the thickness of the outer peripheral wall 21a of the second liquid chamber 21. As shown in Figure 4C, the air chamber 13 is formed as a closed space between the outer tube flange 4 and the inner tube flange 5 in the area where the outer tube 2 and the inner tube 3 are vulcanization bonded with the elastic body 8. However, as shown in Figure 4B, in the portion where the outer tube 2 and the inner tube 3 are not vulcanized and bonded by the elastic body 8, the air chamber 13 is open to the atmosphere through the space between the outer tube 2 and the inner tube 3.

[0028] Next, the flexible member 14 (see FIG. 3) and the first magnetic body 6 (see FIG. 3) that supports the flexible member 14 will be described. First, the first magnetic body 6 will be described. The first magnetic body 6 is made of, for example, iron, cobalt, nickel, or an alloy thereof. 4B, the first magnetic body 6 has a hat shape. That is, the first magnetic body 6 has a protrusion 6a that fits inside the stepped wall 5a of the inner cylinder flange 5, and a disk-shaped flange portion 6b that corresponds to the hat-shaped flange portion. As shown in FIG. 4B, the protruding portion 6a has an opening 6a1 formed therein so as to correspond to the hole 3a of the inner cylinder 3.

[0029] As shown in FIG. 4A, the flange portion 6b of the first magnetic body 6 is formed with a slit S3 corresponding to the slit S1 of the inner cylinder flange 5. As shown in FIG. 4C, the flange portion 6b of the first magnetic body 6 is formed with a slit S4 corresponding to the slit S2 of the inner cylinder flange 5.

[0030] 5B is a partial perspective view of the active vibration isolation device including the VB-VB cross section of FIG. 2. FIG. As shown in Figure 5B, the flange portion 6b of the first magnetic body 6 is formed with an arc-shaped slit S3 corresponding to the second liquid chamber 21 (see Figure 5A) and an arc-shaped slit S4 corresponding to the air chamber 13 (see Figure 5A), which are arranged alternately in the circumferential direction across the partition portion 6b1. In Fig. 5B, reference numeral 15c denotes an orifice of the first liquid chamber 15 formed between the partition portion 6b1 and a flange portion 7b of the second magnetic body 7, which will be described later. This orifice 15c, which is indicated by a hidden line (dotted line) in Fig. 5B, will be described in detail later.

[0031] Next, the flexible member 14 (see FIG. 3) will be described. The flexible member 14 is assumed to be made of synthetic rubber. As shown in FIG. 3, the flexible member 14 has a flexible member main body 14a and a support portion 14b that causes the first magnetic body 6 to support the flexible member main body 14a. As shown in FIGS. 4A and 4C, the flexible member main body 14a is formed in the shape of a film that is thin in the axial direction and extends in the radial and circumferential directions.

[0032] As shown in Fig. 4A, the flexible member main body 14a is disposed so as to close the slit S3 of the first magnetic body 6 (flange portion 6b). As shown in Fig. 4C, the flexible member main body 14a is disposed so as to close the slit S4 of the first magnetic body 6 (flange portion 6b). Specifically, as shown in FIGS. 4A and 4C, the flexible member main body 14a is integrally formed with the support portion 14b so as to be located in the middle of the flange portion 6b in the thickness direction.

[0033] As shown in FIGS. 4A and 4C, the support portion 14b is formed of a film body that is vulcanization bonded to the flange portion 6b so as to sandwich the flange portion 6b from the front and back. As shown in Figures 4A to 4C, the support portion 14b is formed to cover almost the entire front and back of the flange portion 6b, except for the outer peripheral edge of the flange portion 6b and the portion where the orifice 15c (see Figure 4B) of the first liquid chamber 15 (see Figure 4B) described below is formed. The support portions 14b extending from the front and back of the flange portion 6b are joined together with the inner peripheral edges of the slits S3 (see Figure 4A) and S4 (see Figure 4C) and support the flexible member main body 14a (see Figures 4A and 4C).

[0034] Next, the second magnetic body 7 (see FIG. 3) will be described. The second magnetic body 7 is made of, for example, iron, cobalt, nickel, or an alloy thereof. As shown in Fig. 3, the second magnetic body 7 has a cylindrical portion 7a and a flange portion 7b extending radially outward from one axial end of the cylindrical portion 7a. The outer diameter of the flange portion 7b is formed to be the same as the outer diameter of the flange portion 6b of the first magnetic body 6, as shown in Fig. 3. As shown in FIG. 4B, a hole 7a1 that communicates with the hole 3a of the inner cylinder 3 via the opening 6a1 of the first magnetic body 6 is formed inside the cylinder portion 7a. Also, as shown in Figure 4B, an annular space is formed between the corner formed by the cylindrical portion 7a and flange portion 7b of the second magnetic body 7 and the protruding portion 6a of the first magnetic body 6, in which an electromagnetic coil 12 (magnetic field generating unit) is housed.

[0035] 4A to 4C, the flange portion 6b of the first magnetic body 6 and the flange portion 7b of the second magnetic body 7 are magnetically insulated by the support portion 14b of the flexible member 14. However, as shown in FIG. 4B, the support portion 14b is omitted from the portion where the orifice 15c of the first liquid chamber 15, which will be described next, is formed.

[0036] As shown in FIGS. 4A and 4C, a first liquid chamber 15 is formed between the flange portion 7b of the second magnetic body 7 and the flexible member main body 14a. That is, the first liquid chamber 15 shown in Figure 5B has a first liquid chamber 15a that is adjacent to the second liquid chamber 21 (see Figure 4A) in the axial direction via the flexible member main body 14a (see Figure 4A), and a first liquid chamber 15b that is formed so as to be adjacent to the air chamber 13 (see Figure 4C) in the axial direction via the flexible member main body 14a (see Figure 4C). The first liquid chamber 15b corresponds to the "first liquid chamber that is not adjacent to the second liquid chamber" in the claims.

[0037] As shown in FIG. 4B, an orifice 15c of the first liquid chamber 15 is formed between the flange portion 6b of the first magnetic body 6 corresponding to the partition portion 6b1 (see FIG. 5B) and the second magnetic body 7.

[0038] 5C is a partial perspective view of the active vibration isolation device including the VC-VC cross section of FIG. 2. FIG. As shown in FIG. 5C, the first liquid chamber 15 is continuous in an annular shape in a cross section including the orifice 15c. As described above, the first liquid chamber 15a and the first liquid chamber 15b shown in FIG. 5B are connected by the orifice 15c. The first liquid chamber 15 is filled with a magnetorheological fluid 20b. As the magnetorheological fluid 20b, known magnetorheological fluids such as MRF (Magneto-Rheological Fluid) and MRC (Magneto-Rheological Compound) in which magnetic powder is dispersed in mineral oil or synthetic oil can be suitably used.

[0039] The electromagnetic coil 12 (magnetic field generating unit) is formed in a ring shape as shown in Fig. 3. As will be described later, the electromagnetic coil 12 generates a magnetic field that forms a magnetic path Mc (see Fig. 6D) that passes through the magnetorheological fluid 20b (see Fig. 6D) in the orifice 15c (see Fig. 6D). As shown in FIG. 3, the spacer 9 is formed of a ring member having an outer diameter equal to the outer diameter of the flange portion 7b of the second magnetic body 7. As shown in FIG. 4B, the spacer 9 is disposed between the outer circumferential edge of the flange portion 6b of the first magnetic body 6 and the outer circumferential edge of the flange portion 7b of the second magnetic body 7. Such a spacer 9 maintains a constant axial width of the orifice 15c formed between the flange portion 6b and the flange portion 7b.

[0040] <<Operation of the active vibration isolation device>> Next, the operation of the active vibration isolation device 1 will be described. FIG. 6A is an explanatory diagram of the operation of the active vibration damping device 1 when vibrations or the like are input in the axial direction of the active vibration damping device 1. FIG. 6B is an explanatory diagram of the operation of the active vibration damping device 1, showing how the magnetorheological fluid 20b flows in the first liquid chamber 15 when vibrations or the like are input in the axial direction of the active vibration damping device 1. FIG. 6C is an explanatory diagram of the operation of the active vibration damping device 1 when vibrations or the like are input in a direction that scoops out the inner cylinder 3 of the active vibration damping device 1 relative to the outer cylinder 2. FIG. 6D is an explanatory diagram of the operation of the active vibration damping device 1, showing how a magnetic path Mc is formed by the magnetic field generated by the electromagnetic coil 12. FIG. 6E is a schematic diagram showing the operation of the magnetic powder Mp when a magnetic field is applied to the orifice 15c of the first liquid chamber 15.

[0041] First, the operation of the active vibration isolation device 1 when the electromagnetic coil 12 (see FIG. 6A) is not energized will be described. As shown in FIG. 4C, in the active vibration isolation device 1, the inner cylinder 3 is elastically supported by an elastic body 8 within the outer cylinder 2. Therefore, in the active vibration isolation device 1, as shown in FIG. 6A, when an external force such as a load or vibration amplitude is input to the inner cylinder 3 in the axial direction indicated by the white arrow, the relative positions of the inner cylinder 3 and the outer cylinder 2 are displaced.

[0042] 6A, when an external force is applied in the direction of the white arrow, assuming that the inner cylinder 3 is displaced downward on the paper, the outer cylinder flange 4 presses the elastic body 8 that defines the second liquid chamber 21 between itself and the inner cylinder flange 5. This increases the liquid pressure of the liquid 20a in the second liquid chamber 21. When the liquid pressure of the liquid 20a in the second liquid chamber 21 increases, the liquid 20a presses the flexible member main body 14a of the flexible member 14 toward the first liquid chamber 15 side.

[0043] As described above, the first liquid chamber 15a shown in Figure 5B is adjacent to the second liquid chamber 21 (see Figure 4A) and is connected to the first liquid chamber 15b via the orifice 15c. The first liquid chamber 15b is adjacent to the air chamber 13 (see Figure 4C) as described above. As shown in FIG. 4B, the air chamber 13 is open to the atmosphere, and therefore the flexible member main body 14a of the flexible member 14 that separates the first liquid chamber 15 and the air chamber 13 shown in FIG. 4C is pressed toward the air chamber 13.

[0044] 6A is displaced upward in the plane of the drawing, the outer cylinder flange 4 pulls the elastic body 8 that defines the second liquid chamber 21 between itself and the inner cylinder flange 5. This reduces the liquid pressure of the liquid 20a in the second liquid chamber 21.

[0045] When the liquid pressure of the liquid 20a in the second liquid chamber 21 decreases, the liquid 20a pulls the flexible member main body 14a of the flexible member 14 toward the second liquid chamber 21 side. As a result, the flexible member main body 14a of the flexible member 14 shown in FIG.

[0046] Then, with the displacement of the flexible member main body 14a caused by the displacement of the inner cylinder 3 shown in FIG. 6A, the magnetorheological fluid 20b filled in the first liquid chamber 15 generates a flow F passing through the orifice 15c, as shown in FIG. 6B. The active vibration isolation device 1 exhibits a damping characteristic for input vibrations and the like due to the flow resistance when the magnetorheological fluid 20b passes through the orifice 15c.

[0047] As described above, the inner cylinder 3 (see FIG. 4C) is elastically supported within the outer cylinder 2 (see FIG. 4C) and is swingable within the outer cylinder 2. 6C assumes that axis P is perpendicular to axis Ax and extends along the longitudinal direction of the oval track-shaped cross section of inner cylinder 3. FIG. 6C shows the active vibration isolation device 1 in which inner cylinder 3 rotates around axis P. As shown in FIG. 6C, the second liquid chamber 21 is formed on the flat outer surface of the inner cylinder 3, i.e., on the side that is not directly vulcanized and bonded to the inner peripheral surface of the outer cylinder 2 by the elastic body 8.

[0048] 6C, when an external force such as vibration displaces the inner cylinder 3 so as to gouge outward from the outer cylinder 2, the inner cylinder 3 rotates around the axis P. At this time, the outer cylinder flange 4 on the side having the second liquid chamber 21 alternately displaces toward or away from the inner cylinder flange 5 on both sides of the axis Ax. The liquid 20a in the second liquid chamber 21 is pressurized or depressurized. As a result, the magnetorheological fluid 20b filled in the first fluid chamber 15 generates a flow F passing through the orifice 15c, as shown in FIG. 6B. The active vibration isolation device 1 exhibits a damping characteristic for input vibrations and the like due to the flow resistance when the magnetorheological fluid 20b passes through the orifice 15c.

[0049] Next, the operation of the active vibration isolation device 1 (see FIG. 6D) when the electromagnetic coil 12 (see FIG. 6D) is energized will be described. As shown in FIG. 6D, a magnetic field generated by the energized electromagnetic coil 12 forms a magnetic path Mc in the first magnetic body 6 and the second magnetic body 7 through the magnetorheological fluid 20b in the orifice 15c.

[0050] As shown in the left diagram in FIG. 6E, the magnetorheological fluid 20b in the orifice 15c of the first liquid chamber 15 maintains the dispersed state of the magnetic powder Mp and exhibits the desired fluidity when no magnetic field is applied. In contrast, as shown in the right diagram of Fig. 6E, when a magnetic path Mc (see Fig. 6E) is formed by the generated magnetic field, the magnetic powder particles Mp are aligned along the magnetic flux ML. As a result, the apparent viscosity of the magnetorheological fluid 20b increases, and the aligned magnetic powder particles Mp act as valve bodies, generating flow resistance within the orifice 15c. The active vibration isolation device 1 exhibits damping characteristics for input vibrations and the like due to the flow resistance of the magnetorheological fluid 20b in this orifice 15c. The damping characteristics of this vibration or the like can be varied by controlling the value of the current flowing through the electromagnetic coil 12 (see FIG. 6D) according to the magnitude of the input vibration or the like.

[0051] The active vibration damping device 1 of this embodiment is configured to cause a flow of the magnetorheological fluid 20b in the first liquid chamber 15 in response to a change in the liquid pressure of the liquid 20a in the second liquid chamber 21 when an external load or vibration amplitude is applied to the outer cylinder 2 or the inner cylinder 3 in the axial direction, or when an external load or vibration amplitude is applied so that the inner cylinder 3 is gouged within the outer cylinder 2. The active vibration damping device 1 controls the damping characteristics of vibrations, etc. by the magnitude of the magnetic field (magnetic flux density) applied to the orifice 15c of the first liquid chamber 15.

[0052] Unlike conventional active vibration damping devices (see, for example, Patent Document 1) that directly convert input such as external vibrations into a flow of magnetorheological fluid, this active vibration damping device 1 causes a flow of magnetorheological fluid 20b in the first liquid chamber 15 by changing the liquid pressure of liquid 20a in the second liquid chamber 21.

[0053] <Action and effect> Next, the effects of the active vibration isolation device 1 according to this embodiment will be described. The active vibration damping device 1 of this embodiment has an outer tube 2, an inner tube 3 arranged on the inner side of the outer tube 2, an electromagnetic coil 12 (magnetic field generating unit) that generates a magnetic field, a first magnetic body 6 and a second magnetic body 7 that form a magnetic path Mc by the magnetic field, a first liquid chamber 15 filled with a magnetorheological fluid 20b, and a second liquid chamber 21 adjacent to the first liquid chamber 15 and filled with a liquid 20a. The active vibration damping device 1 also includes an outer tube flange 4 extending radially outward from one axial end of the outer tube 2, and an inner tube flange 5 extending radially outward from the inner tube 3 and positioned axially apart from the outer tube flange 4. The first liquid chamber 15 and the second liquid chamber 21 of the active vibration damping device 1 are separated in the axial direction by a flexible member 14. The second fluid chamber 21 of the active vibration damping device 1 is formed so as to be sandwiched between the inner cylinder flange 5 and the outer cylinder flange 4 . A part of the first fluid chamber 15 forms a flow path for the magnetorheological fluid 20b located on the magnetic path Mc.

[0054] In other words, the active vibration damping device 1 of this embodiment is configured so that when an external force such as vibration is input in the axial direction through at least one of the outer tube 2 and the inner tube 3, the liquid pressure of the liquid 20a filled in the second liquid chamber 21 changes due to relative displacement between the outer tube flange 4 and the inner tube flange 5. Unlike conventional active vibration damping devices (see, for example, Patent Document 1) that directly convert external inputs such as vibrations into a flow of magnetorheological fluid, the active vibration damping device 1 of this embodiment is configured to cause a flow of magnetorheological fluid 20b in the first liquid chamber 15 by changing the liquid pressure of liquid 20a in the second liquid chamber 21, as described above.

[0055] According to such an active vibration isolation device 1, it is possible to change the rigidity while maintaining good response performance to vibrations input in the axial direction and vibrations that scoop out the inner cylinder 3 within the outer cylinder 2.

[0056] Furthermore, with such an active vibration damping device 1, the response performance to input vibrations, etc. can be improved by increasing the volume of the second liquid chamber 21 filled with liquid 20a without increasing the volume of the first liquid chamber 15 filled with magnetorheological fluid 20b.

[0057] Furthermore, according to the active vibration damping device 1, unlike conventional active vibration damping devices (see, for example, Patent Document 1), the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, so that the amount of magnetorheological fluid 20b used, which is relatively heavy and expensive and contains magnetic powder Mp, can be reduced.

[0058] Furthermore, according to the active vibration damping device 1, unlike conventional active vibration damping devices (see, for example, Patent Document 1), the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, thereby reducing the absolute amount of magnetic powder Mp contained in the magnetorheological fluid 20b that settles.

[0059] Furthermore, according to the active vibration damping device 1, the volume of the liquid chamber (first liquid chamber 15) filled with the magnetorheological fluid 20b can be made relatively small, so that the settled magnetic powder Mp can be redispersed by the stirring action of the flow F of the magnetorheological fluid 20b. Furthermore, the active vibration isolation device 1 can suppress the precipitation of magnetic powder Mp over time, and therefore can maintain good vibration and other damping performance.

[0060] In addition, the active vibration damping device 1 of this embodiment has multiple second liquid chambers 21 (see Figure 5A) and air chambers 13 (see Figure 5A) arranged alternately in the circumferential direction, and multiple first liquid chambers 15 (see Figure 5B) are provided adjacent to and corresponding to these second liquid chambers 21 and air chambers 13 in the axial Ax direction, and the multiple first liquid chambers 15 are connected to each other in the circumferential direction by orifices 15c (see Figure 5B). Specifically, the active vibration damping device 1 has at least four first liquid chambers 15a, 15b (see Figure 5B) arranged along the circumferential direction, and the second liquid chamber 21 (see Figure 5A) is arranged adjacent to two of the at least four first liquid chambers 15a, 15b (see Figure 5B) that are located on opposite sides of the axis Ax, and the first liquid chamber 15a adjacent to the second liquid chamber 21 and the first liquid chamber 15b that is not adjacent to the second liquid chamber 21 are connected by an orifice 15c located on the magnetic path Mc.

[0061] With such an active vibration damping device 1, the rigidity can be varied not only against the input of external forces in the direction of axis Ax, but also against the input of external forces that cause a displacement (gouging) that causes the pair of second liquid chambers 21 to tilt in the direction in which they are aligned around axis Ax (for example, in the left-right direction when used as bushings 35 of the subframe 30 shown in Figure 1). Furthermore, in this active vibration damping device 1, the first liquid chamber 15a is connected by the orifice 15c to the first liquid chamber 15b that is not adjacent to the second liquid chamber 21, i.e., the first liquid chamber 15b that is adjacent to the air chamber 13, and therefore does not impede the displacement of the flexible member 14 (flexible member main body 14a). The formation of the flow F of the magnetorheological fluid 20b between the first liquid chambers 15a, 15b via the orifice 15c is highly sensitive to the input of external force.

[0062] In addition, this active vibration damping device 1 further includes an elastic body 8 arranged between the outer tube 2 and the inner tube 3 and between the outer tube flange 4 and the inner tube flange 5, and in the elastic body 8, a second liquid chamber 21 is formed and an air chamber 13 is further formed, and the first liquid chamber 15 and the air chamber 13 are separated in the axial Ax direction by a flexible member 14 (flexible member main body 14a). According to such an active vibration isolation device 1, the elastic body 8 itself can exert a good damping performance for vibrations and the like. Furthermore, with such an active vibration isolation device 1, the flow F of the magnetorheological fluid 20b is more effectively formed in response to the input of an external force due to the action of the elastic body 8 itself.

[0063] In addition, in this active vibration damping device 1, the first liquid chamber 15b, which is not adjacent to the second liquid chamber 21, is adjacent to the air chamber 13 via the flexible member 14 (flexible member main body 14a), and the air chamber 13 has a connecting wall 13a that extends circumferentially on the outer periphery of the flexible member 14 (flexible member main body 14a) and is connected to the outer periphery wall 21a that forms the second liquid chamber 21. According to such an active vibration isolation device 1, the intrusion of foreign matter such as dust into the air chamber 13 can be prevented by the connecting wall 13a.

[0064] The active vibration damping device 1 of this embodiment can be suitably used in place of various conventional mount bushes and suspension bushes, which must be carefully selected taking into account safety performance, driving performance, comfort performance, ride comfort performance, etc.

[0065] Although the present embodiment has been described above, the present invention is not limited to the above embodiment and can be embodied in various forms. In the embodiment described above, as shown in Fig. 5A, the active vibration damping device 1 is provided with two second liquid chambers 21 and two air chambers 13. The second liquid chambers 21 and the air chambers 13 are arranged alternately in the circumferential direction.

[0066] As shown in Figure 5B, this active vibration damping device 1 has two first liquid chambers 15a adjacent to the second liquid chamber 21 (see Figure 5A) in the axial Ax direction, and two first liquid chambers 15b adjacent to the air chamber 13 (see Figure 5A) in the axial Ax direction. As shown in FIG. 5B, the first liquid chambers 15a and 15b are arranged alternately in the circumferential direction and are connected to each other by four orifices 15c that form part of the first liquid chamber 15.

[0067] That is, in the active vibration damping device 1 of the above embodiment, multiple second liquid chambers 21 and air chambers 13 are arranged alternately in the circumferential direction, and multiple first liquid chambers 15a, 15b are provided adjacent to these second liquid chambers 21 and air chambers 13 in the axial Ax direction, and the multiple first liquid chambers 15a, 15b are connected to each other in the circumferential direction by orifices 15c.

[0068] (First Modification) Figure 7A is a layout diagram of the second liquid chamber 21 and air chamber 13 of the active vibration damping device 1 according to the first modified example. Figure 7B is a layout diagram of the first liquid chambers 15a, 15b of the active vibration damping device 1 according to the first modified example. Note that in this first modified example, the same components as those in the above embodiment are given the same reference numerals and detailed explanations thereof will be omitted.

[0069] As shown in FIG. 7B, the active vibration damping device 1 according to the first modified example includes eight first liquid chambers 15 (first liquid chambers 15a, 15b) arranged in the circumferential direction. 7A, the second liquid chambers 21 of the active vibration damping device 1 according to the first modified example are located on two straight lines X and Y that are perpendicular to the axis Ax. That is, as shown in FIG. 7B, the second liquid chambers (see FIG. 7A) are provided at positions adjacent to the axis Ax direction to the four first liquid chambers 15a that are located on the two straight lines X and Y that are perpendicular to the axis Ax. As shown in FIG. 7A, the air chambers 13 of the active vibration damping device 1 according to the first modified example are arranged alternately with the second liquid chambers 21 in the circumferential direction.

[0070] 7B, in the active vibration damping device 1 according to the first modified example, the first liquid chamber 15a and the adjacent first liquid chamber 15b corresponding to the air chamber 13 in the axial Ax direction are connected by an orifice 15c that is part of the first liquid chamber 15. The first liquid chamber 15b corresponds to the "first liquid chamber that is not adjacent to the second liquid chamber" referred to in the claims. The orifice 15c is located on the magnetic path Mc (see FIG. 6D) in the same manner as in the previous embodiment. In FIG. 7A, reference numeral 20a denotes a liquid, and in FIG. 7B, reference numeral 20b denotes a magnetorheological fluid.

[0071] According to the active vibration isolation device 1 of the first modified example, the rigidity can be varied with even better response to the input of an external force that causes the inner cylinder 3 to dig into the outer cylinder 2.

[0072] (Second Modification) 8 is a diagram illustrating the configuration of an active vibration isolation device 1 according to a second modified example. In this second modified example, the same components as those in the above embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted. As shown in Figure 6A, in the active vibration damping device 1 of the above embodiment, the second liquid chamber 21 is formed only between the outer tube flange 4 and the inner tube flange 5, and is not formed between the outer tube 2 and the inner tube 3.

[0073] In contrast, in the active vibration damping device 1 according to the second modified example, as shown in FIG. 8, the second liquid chamber 21 is formed so as to extend to the inside of the elastic body 8 arranged between the outer tube 2 and the inner tube 3. In Figure 8, symbol 14a denotes the flexible member body of the flexible member 14 that separates the first liquid chamber 15 and the second liquid chamber 21, symbol 6 denotes a first magnetic body, symbol 7 denotes a second magnetic body 7, symbol 12 denotes an electromagnetic coil (magnetic field generating part), symbol 9 denotes a spacer 9, symbol 20a denotes a liquid, and symbol 20b denotes a magnetorheological fluid.

[0074] 8, the liquid pressure of the liquid 20a in the second liquid chamber 21 changes with high sensitivity not only in the axial direction but also in the radial direction (direction perpendicular to the axis) relative to the displacement of the outer cylinder 2 and the inner cylinder 3. The active vibration damping device 1 can vary its rigidity with high sensitivity in response to the input of external forces in the axial and radial directions (directions perpendicular to the axis).

[0075] (Third Modification) Fig. 9A is a vertical cross-sectional view of an active vibration isolation device 1 according to a third modified example. Fig. 9B is an exploded perspective view of an active vibration isolation device 1 according to the third modified example. In this third modified example, the same components as those in the above embodiment are given the same reference numerals, and detailed descriptions thereof will be omitted. As shown in Figure 9A, in the active vibration damping device 1 of the third modified example, when the inner tube 3 is displaced in the axial Ax direction inside the outer tube 2, the liquid pressure of the liquid 20a in the second liquid chamber 21 formed in the elastic body 8 sandwiched between the outer tube flange 4 and the inner tube flange 5 changes. In the first liquid chamber 15 formed in the axial Ax direction relative to the second liquid chamber 21 via a flexible member 14, the liquid pressure of the magnetorheological fluid 20b filled therein changes in accordance with changes in the liquid pressure of the liquid 20a in the second liquid chamber 21.

[0076] On the other hand, as shown in Figure 9B, the active vibration damping device 1 of the third modified example differs from the active vibration damping device 1 of the above embodiment (see Figure 5A) in that one second liquid chamber 21 and one air chamber 13 are arranged circumferentially.

[0077] Furthermore, the active vibration damping device 1 according to the third modified example is provided with one first liquid chamber 15a so as to correspond to and be adjacent to the second liquid chamber 21 in the direction of the axis Ax. Furthermore, the active vibration damping device 1 according to the third modified example is provided with one first liquid chamber 15b so as to correspond to and be adjacent to the air chamber 13 in the direction of the axis Ax. The first fluid chambers 15a and 15b are connected to each other by two orifices 15c in the circumferential direction. In the active vibration damping device 1 of the third modified example, as shown in Figure 9A, when the inner cylinder 3 is displaced in the axial Ax direction, a flow F of the magnetorheological fluid 20b is generated between the first liquid chambers 15a and 15b through the orifice 15c, as shown in Figure 9B.

[0078] The active vibration isolation device 1 exhibits a damping characteristic for input vibrations and the like due to the flow resistance when the magnetorheological fluid 20b passes through the orifice 15c. Furthermore, as shown in Figure 9A, in the active vibration damping device 1, a magnetic path Mc is formed between the first magnetic body 6 and the second magnetic body 7 through the magnetorheological fluid 20b within the orifice 15c due to the magnetic field of the energized electromagnetic coil 12 (magnetic field generating unit). In Figure 9B, symbol 2 is an outer tube, symbol 3 is an inner tube, symbol 4 is an outer tube flange, symbol 5 is an inner tube flange, symbol 8 is an elastic body, and symbol 21 is a second liquid chamber filled with liquid 20a. Also, in Figure 9B, symbol 14a is the flexible member main body of flexible member 14, symbol 14b is the support part of flexible member 14, symbol 6 is the first magnetic body, symbol 7 is the second magnetic body 7, and symbol 12 is the electromagnetic coil (magnetic field generating part).

[0079] According to the active vibration isolation device 1 of the third modified example, the rigidity can be made variable with respect to the input of an external force in the axial direction with a simpler configuration. [Explanation of symbols]

[0080] 1. Active vibration isolation device 2 outer cylinder 3 Inner cylinder 4 Outer cylinder flange 5 Inner cylinder flange 6 First magnetic body 7 Second magnetic body 12 Electromagnetic coil (magnetic field generating part) 13 Air chamber 13a Connecting wall 14 Flexible member 15 1st liquid chamber 15a 1st liquid chamber 15b 1st liquid chamber 15c Orifice 20a liquid 20b Magnetorheological fluid 21 2nd liquid chamber 21a Outer wall Mc magnetic path

Claims

1. An outer cylinder and an inner cylinder disposed on the inner circumferential side of the outer cylinder; a magnetic field generating unit that generates a magnetic field; a magnetic body that forms a magnetic path by the magnetic field; a first fluid chamber filled with a magnetorheological fluid; a second liquid chamber adjacent to the first liquid chamber and filled with liquid; An active vibration isolation device having an outer cylinder flange extending radially outward from one axial end of the outer cylinder; an inner cylinder flange extending radially outward from the inner cylinder and spaced apart from the outer cylinder flange in the axial direction; The first liquid chamber and the second liquid chamber are partitioned in the axial direction by a flexible member, The second fluid chamber is formed to be sandwiched between the inner cylinder flange and the outer cylinder flange, An active vibration isolation device, characterized in that a part of the first fluid chamber forms a flow path for the magnetorheological fluid located on the magnetic path.

2. At least four first liquid chambers are provided along the circumferential direction, the second liquid chambers are provided at positions adjacent to two of the at least four first liquid chambers that are located on opposite sides of the axis of the inner cylinder, An active vibration damping device as described in claim 1, characterized in that the first liquid chamber adjacent to the second liquid chamber and the first liquid chamber not adjacent to the second liquid chamber are connected by an orifice that is part of the first liquid chamber located on the magnetic path.

3. At least eight first liquid chambers are provided along the circumferential direction, the second liquid chambers are provided at positions adjacent to the four first liquid chambers located on two straight lines perpendicular to the axis of the inner cylinder, An active vibration damping device as described in claim 2, characterized in that the first liquid chamber adjacent to the second liquid chamber and the first liquid chamber not adjacent to the second liquid chamber are connected by an orifice that is part of the first liquid chamber located on the magnetic path.

4. an elastic body disposed between the outer cylinder and the inner cylinder and between the outer cylinder flange and the inner cylinder flange; The elastic body has the second liquid chamber formed therein and also an air chamber formed therein, 2. An active vibration isolation device according to claim 1, wherein the first liquid chamber and the air chamber are separated in the axial direction by a flexible member.

5. the first liquid chamber not adjacent to the second liquid chamber is adjacent to an air chamber via a flexible member; 4. An active vibration isolation device according to claim 2, wherein the air chamber includes a connecting wall that extends circumferentially on the outer periphery of the flexible member and is connected to an outer periphery wall that forms the second liquid chamber.

6. 4. The active vibration isolation device according to claim 1, wherein the second fluid chamber extends to a space between the outer cylinder and the inner cylinder.

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